Field of the Disclosure
The present disclosure relates to cellular networking and, specifically, to joint wireless and fixed network optimization for heterogeneous cellular networks.
Description of the Related Art
As cellular networks that provide wireless network access to mobile user devices have been further developed over the years, new generations of cellular networking standards have been implemented about every decade since the first generation (1G) systems were introduced. As each new generation appears, different frequency bands and new transmission technology has enabled higher data rates to be provided via cellular networking.
In a traditional cellular network, such as up to the third generation (3G) systems, radio frequency (RF) components and a fixed network (often an optical network) to link the RF components have typically been viewed as individual and separate systems that may be separately designed and implemented. Underlying this design approach has often been the assumption that, for any given set of traditional cellular RF components, the fixed network would have sufficient throughput capacity to accommodate the resulting bandwidth demand. Furthermore, because such traditional cellular networks have been comprised of so-called “large cells” (including so-called “macrocells” and “microcells”) that are relatively few in number, the access to and availability of the fixed network for cell base stations has not generally been a feasibility constraint for a given cellular network design. Therefore, for such a traditional cellular network design, RF engineers could primarily focus on radio considerations to design cell placements and optimal coverage for a given service area.
Advancements in 3G systems have included a distributed base station architecture in which a remote radio head (RRH) was separated from a baseband unit (BBU) in a base station using an optical fiber (or sometimes a microwave link) for more flexible network design and rollout. The network segments that connect standalone RRHs with centralized BBUs at cell locations are referred to as a “fronthaul” network in the distributed base station architecture, while a “backhaul” network refers to the network that interconnects BBUs.
Recently, post-3G cellular network systems have been widely adopted, such as Long Term Evolution (LTE), and continue to grow rapidly. Many new radio access network (RAN) technologies and wireless topologies continue to be developed for LTE, including so-called heterogeneous wireless network architectures that include numerous so-called “small cells” (including so-called “picocells” and “femtocells”). Because the number of small cells in a heterogeneous cellular network may be much larger than the number of large cells in traditional cellular network architectures, heterogeneous designs may be relatively complicated due to the factors of optimal radio coverage with minimal interference and accessibility of each small cell to the fronthaul or backhaul network, among other factors.
Furthermore, new cloud-RAN (C-RAN) cellular wireless network architectures are being used that provide further advantages from implementing LTE-Advanced features, such as Coordinated MultiPoint (CoMP) and Inter-Cell Interference Coordination (ICIC), which rely on inter-cell communication and coordination to improve performance of cells that may provide an economic benefit to the overall cellular network. Because new features such as CoMP, ICIC and Enhanced ICIC (eICIC), rely on very tight timing synchronization, low latency, and very high bandwidth in the wireless domain, certain performance demands on emerging fronthaul networks may approach or exceed those of the backhaul network.
Accordingly, the availability of a suitable fixed network to support emerging cellular network topologies, such as C-RAN, may no longer be a valid assumption for every proposed cell in a given network design. Conversely, RF issues, such as interference, may limit the utilization of high performance fronthaul or backhaul networks (referred to collectively as “x-haul” herein), resulting in wasted network capacity that is economically undesirable.